Process for isomerizing a low-boiling isomerizable saturated hydrocarbon



Feb, 15, 1949.

\ F. E. FREY PROCESS FOR ISOMERIZING A LOW-BOILING ISOMERIZABLE SATURATED HYDROCARBON Filed Nov. 25, 1943 mOODJw am: M

Nwn'ioa Nnusd aazmvmadao uazmvmaaoslacl uazlNvinaosmG uQLvNollavad NN 2102 mI-UvOmm lNVENTOR FREDERICK E .FREY

n ,si ATTO Nl-:Ys

- Marcnll, 1940, now Patent'2,3`17,90l issued' April Patented Feb. 15, v1949 l v I l l. This-inventionrelates'to Athe reconstruction off hydrocarbons. In a specific em'loiilimen-t" it'J rel` lates to' the reconstruction of' saturtdlliyd carbosin the presence of" acatalystfcompris gef a Hmajorpropotion 0"" concentrated: hydfroU uoricacidj and` vay rninni" proportie uoride This' application isla continu partici: my coperidingI application'fserial: No'. 460,- s67',' f1'1ed on octoers; Y1942; which in tuljriisa continuatibn-inpart of my' copentiirg'applia" mori-sensi No.' 426,527, mee-January 21,13; m42; noW'Patent`2A0359; granted: July 9;"19462 latter' application is" inf turn 'a' contiiiiaft "r`1"" pa'ito 'my' application Serial No'. 3231443? filed" cartn: an

@his tsm close' that; in the presence of substantiapiop r'g otherreaction Pvshicli tionjsfv of hydrofluor'ic acid' and under siiitalle-| l neioddis conditions` of tinie andfte'mpeature," saturated' hydrocarbons are' reconstructed 'to lclydrfocarbons of' ydifferentcarbor:l=s1e1etoriv arrangement' and.` different bolirigpoint. Par'anic' li"yclr'ocar'lociis, l for example', undergo 'conversion t isomers andf` also"undergofconversin to hydrocabonsofbotli" lowerl and; higher noleculai` Weights'ani' 'cor-J hydrocarbons using hydrogenv uoride'A 'as theY versioni' of a drastic type, with vfrattiife ofthe carbon skeleton and with consumptionA fjorlf lowand econiiicalaniont's' of BFS as' wellas'HF; f

Still another Object of my invention is' toiedcej 50 the formation o'f siudginthereostiiuctiori oft atmospheric temperature or at a temprature only somewhat higher than atmospheric temperature. In its preferred form my catalyst comprises a homogeneous liquid solution of boron fluoride in a large excess of liquid hydroiiuoric acid'. In determining the so-called K constants of solutions of boron trifluoride in liquid anhydrous hydrouoric acid it has been determined that there appears to be primarily a true solutionv of boron triuoride in the liquid hydrofiuoric acid. However, 4an induction period has been observed which, in certain instances, has been eliminated by the addition of reactive hydrocarbons, such as oleiins. Alsopcomplexes between hydrocarbons and the catalyst ingredients have been found'in the catalyst phase after use. In a still further preferred modification of my invention I include in this catalytic mixture a small amountjof water since, as will `be shown hereinafter by data obtained in making comparative runs,'the use of strictly anhydrous hydrofluoric acid and a minor amount of boron triuoride as the catalyst is attended with the formation of an appreciable amount Vof organic sludge. sludge does not make the use of an anhydrous catalyst impractical or uneconomical but, as can readily be appreciated, is undesirable. I have now found that when the catalyst is not strictly anhydrous, but contains a small amount of water, there is a much smaller amount of sludge formed and at times the amount of .sludge is practically negligible.

An understanding of various aspects of my invention may be aided by referring to the accompanying drawing and the following discussion thereof. The .drawing is a schematic ow diagram showing one arrangement of apparatus which may be used in the practice of one embodiment of the invention. In order that the discussion may be suiciently specific to be clear the embodiment discussed will be limited to the reconstruction of normal pentane, which will include bothisomerization to form isopentane and amount greater than aboutY l Aper cent by weight. In most instances satisfactory and eflicient operation is obtained when the amount of boron trin fluoride is between about l and about 5 per cent This disproportionation to form butanes and hydro- I carbons having more than live carbon atoms per molecule which will be primarily hexanes. However,.by suitably controlling the reaction conditions, particularly by adding modiers such as free hydrogen, cyoloparaflins and the like, the reaction can be controlled to effect increased amounts of isomerization at the expense of disproportionation. As will be appreciated, the invention may also be applied to other saturated hydrocarbons as herein discussed. y

Referring now to the drawing, normal pentane, preferably in the liquid phase, is introduced through inlet I0 to reactor H. Concentrated hydroiiuoric acid is introduced through inlet I2 and conduit 32, also preferably in the liquid phase, and a minor amount of boron triuoride-is introduced through inlet I3 and passes through conduits I2 and 32 to reactor Il. Although it is not definitely established that the reactions will not take place with both the hydrocarbons and cataweight of the-hydroiiuoric acid, I have found that little benetis to be-derived from having the by weight. Such a composition is a very active catalyst, particularly for treating pentanes and heavier hydrocarbons at about atmospheric temperature, while at the same time the amount of boron trifluoride present is sufciently low that excessive costs for replacing and regenerating the Acatalyst are not incurred, and that excessive pressures are not necessary in order to keep a liquid phase operation, and further extensive corrosion of the usual materials for construction of the reaction vessels such as ordinary steels is not unduly high. Substantially more drastic reaction conditions are necessary in effecting the reconstruction ofbutane and successful operation is generally obtained only by using a somewhat higher proportion of boron trifluoride together with somewhat higher temperatures and longer reaction times. In many instances the proportion of boron triiiuoride which is used will be to some extent correlated with the other reaction conditions and in general a lower reaction temperature may be used with somewhat higher concentrations of boron trifluoride and also a shorter reaction time will be satisfactory with somewhat higher |concentrations oi boron trifluoride.

As previously mentioned a small amount of water is also employed to obtain the most satisfactory operation. This Water may be added directly to reactor l I through conduit 8, or may be added at least in part to the hydrocarbon charge by means of conduit 9 which leads from conduit 8 to conduit IO. Although the necessary amount of water can be included in the hydrofluoric acid introduced through conduit l2, the other manner of operation is preferred. Often a satisfactory amount of water can be maintained in the reaction system after the operation has started by partially or completely saturating the liquid hydrocarbon material charged through conduit I 0 with dissolved water. The concentration of water in the reactor should :be at least about 0.05 per cent by weight of the hydrofluoric acid-boron iiuoride catalyst and generally need notexceed about 1.0 per cent by weight, although in some instances higher concentrations may be found to be desirable. However, the amount of water used should not exceed the molecular equivalent of boron triuoride present since it appears that the water immediately disappears as such through the formation of a complex with the boron triiiuoride, and an appreciable amount of free boron trifluoride must be present to eect the reconstruction reactions at a desirably rapid rate in the preferred temperature range. With added water the amount of boron trifluoride present in excess of that molecularly equivalent to the Water should be within the ranges hereinbefore discussed, namely at least about 0.1 per cent by weight and preferably about l to about 5 per cent by weight, or somewhat more in some instances.

y the length of the reaction zone.

When the reaction is carried lout in a long reaction zone of restricted cross-sectional area, as in a tube coil, it may be found desirable to add Water and/or boron triuoride at various points along The relative proportions of catalyst and hydrocarbon are within a wide range notgreatly critical. Good results are obtained using a hydrocarbon to catalyst weight ratio in the range of about 0.1:1 to 3:1 or

more, and preferably this ratio should be within the range of about 0.5:1 to 1.521. In any event it desirable to entrate 'under conditione; cti-f teuiueretllre-r. bressuire; and; con.contrat.ionA i such..

that an appreciable amount of a liquid hydrofluoric acid phase is present-in` the reaction zone. The. catalyst and the. hydrocarbon reactants should be.I brought into vand maintained inintimategcontact. andnreferably such Contact is effectedby, mechanical mixing resulting4 msnbstantial emulsiiication oi'.A the two. phases. This,

may be doneby meansoi a ymixing` pump, by passi ri''s of baies, by injectingu'thehydrocarbon charge at a high velocity through a jet into a body of' thereaction mixture, by recircuIatiom. or :the likey ascan be readily eiectedby ,one slsi11ed-initheart.

While the reaction temperaturemay be within alther Wide range as between.aboutizandabout 40,0? F., Satisfactory i operation, is nerierally obtained within a much narrower-range. and; suitabii rapid reaction velocities.: have; been, secured f.

at temperatures within the range ofr about 5 0 to about 250 F. With` other reaction conditions constant the reaction rateis slower at low,I temperatures than at high temperatures and the rate olv spending of the catalyst and the extent of secondary reaction and degradation of the product is greateraathigher'temperatures than at lower -tempera-tures; As-v previously mentioned,y with otherreaction conditions constant the/rate of thereactionsA aresomewhat greater with higher' concentrations or boron trifluoride than withv lower concentrations`,although in most' instances satisfactorilyrapid reaction'. rates are obtained when the concentration of free'boron triluor-ide is not` greater than about 5 per centbyweight.- rEhe reconstructionof normal butaneiand also ofv normal hexane appears to require appreciably more diras,

tic reaction, conditions than those Whichv canV be satisfactorily usedwhen treating normal pentane.

With other reaction conditions` constant the optimum reaction time varies in general more or less inversely with the reactiontemperature.- For temperatures within the above-mentionedJ preferred ranges a satisfactory reaction time will generally be found withinthe range of about 5 to f about 60 minutes; With Very shortA times inretorecover'- and; recycle. to thesystem .desired .6011@ .may be recycled to separator l5 and/or ma massed Ythrousituconduite#3;(concocter. Us; 11n the event.lowfboilinghydrocarbons uchfas ethans and/or: hrcpaueitendto accumula System; abortion ouali; oithisffractionim et removedithrousbiconduit, LBA and-inavfbeftreatedrf stituent. s:. Iiydrocarbon.;material, free. solved hydroiiuoric.; acidis passed ,from

tom; of'. frac,tionatorv lit throughl conduit l il` Y isobutenizer 20. wherefrom'. isobutane isf-distille :Glcrbcad and: is Withdrawnthroush outlet,A Hydrocarbonmaterial is passed rfromV th` of,{deiosbutanizerv Zllfthroughcondu to isopentanizer 23, Whereirom isouentarne; diss-.iy tilled overhead and. isa-Withdrawn through outlet;

2,4-, Atleast apart lof tbismaterialmay be passed,

if desired,v backto reactor Il l from. condu through conduits 4l; anddyillv,i Hydrola terial from the bottom of -deisopentanige s; passed through conduit; 25,5159 depentanizer 26,

y..vvherefrom normal pentane is distilled overhead and@ isrecycled4 through conduit 21" to reactor .,H

action the conversion is relativelyincomplete so that large amounts .of unreacted material are.

made and` in continuous operations there is an unnecessarily heavy load on subsequent separating and recyclingn equipment. If the reaction time is excessively .long secondary reactions be,- come involved to an undesirable extent and the life of the catalyst in terms of quantity of product per unit quantity of catalyst is excessively short.

Satisfactory operations havebeen obtained with a correlation of the reaction conditionsv to give/ as high as 70 to .90.1 percentconversion per pass in the reconstruction of. normal pentane, and as high a to 80 per cent per pass for reconstructing isopentane. However, economicaloperations can be realized with appreciably lower conversions per pass in many instances..

The reactions are not greatly affected by---pressure, but, as previously mentioned, itis preferred ..3 `from a major fraction suitable for blending-in Isohexanes` andother 'normallyfliquidj hydrocarbons are passed from the bottomgof depeyritanizer` 26T-through conduit l28gto rerun column 29;"Where.-

motor fuel is distilled overhead and-is Withd through outlet 3H". This ,fraction may be y J'ected" ltofurther-fractionation and' puriloatiom. if desired. A 'minor fraction, ofrelativelyhigh. boiling material is Withdrawn throughjgoutlet `;i"l. A fraction ofintermediate boiling range maywifj' desired, beremoved 'through conduitj 42 andi', passed to conduit 2l'A and reactori Il.

A heavier catalyst phase is recovered from separator I and is recycled at least inparti-through:

conduit 32rto reactor I'I'; Although with the usef offa small arnountoi water,asrhereinbeforegd cussed, the-.amount of sludge formation, isouite small, with prolonged continuous operationitwill be foundV desirable tosubiect. ao'porti'onzf;oft-trices;` catalyst to purification and/or regenerationtreatll` ment and lfcrgthis purpose .aportion of. itis fpa'ssed from separator l5 throughY conduit 33 togpurificationl equipment illustrated. loyy fractionation. 34. From fractionator 34' a substantially-pure lhydrouric acidy ist removed as an overhead product and kisrecycledthrough,conduitl .ititcvreactor lli.. This fractionwll also contain the free boron tri-1l fluoride contained in the. catalyst :passedjto: ,1a-hefractionator: and Will. Acontain most, if not-all; of the low boiling hydrocarbons whichl aregdsolged inthe catalyst.

`High boiling materiall may be Withdrawn throughout-,let v35e; preferably however, it is'passed through conduitfto heater 3l. Heater 31 heats -the material to a tempenature;'in.thefrangey Qtyabout i to 600 11,.,usuallyrncr-erreferab n the range ot:- about..3,50..to.50.0? Whererwon iiuoroorganic materials are decompose ingtI-IF. Some boronV fluoride.. is also, ated. The heatedand decomposed material then passes through conduit 3 8 to flash,chamberv iflmwheerefrom hydrofluoric acid'v and: bo/ron fluoride vare or siudgeiswithdrwn through' outlet 0. Hy-

drogen uoride may be introduced to 'conduit 36 and/or chamber- 39 during the' decomposition of the high boiling catalyst complex and polymer to 8 Recycling of undesired products may' be employed to increase the ultimate yield of desired products.

Example II increase the amount of BFs released in molecular In another test run, normal hexane and com form. Such a procedure is also disclosed and centrat'ed hydroiiuoric acid to'which has been discussed in my co-pending application Serial No. added 5 2 Weight per cent boron fluoride were 457-954 med December 5. 1942' and 110W ahah shaken together in a closed steel pressure vessel d011ed- 'for v,40 minutes. The temperature was main- I' Wlll be apprelated tha? the drawlng 1S 01.115 10 tained at 180 F. by an electricheater. The rediagfammatlc, and that Sultabe speclfc equip sultinghydrocarbon material was found to have ment for the practice of any modification of my the following composition: invention may be readily designated and designed by one skilled in the art. Although the descrip- Hydrocarbon Weight per cent i tion of the drawing has been limited primarily to f Butanes 0.5 a description and discussion of the reconstruction Pentanes 0.6 of normal pentane, the same principles which are NepheXane 6.5 involved may be readily applied to a reconstruc- Y Dilsopropyl 7.9 tion of other specific saturated hydrocarbons or 2-methylpentane 24.9 hydrocarbon fractions, such as fractions securedfgo 3-methy1pentane 10.5 :from natural or straight-run gasolines, particu- Normal hexane 11.5Y llariy the recycle of fractions of higher and/or Heptanes and octanes 6.2 lower boiling points, or ranges, than the hydro-V Hcavier 1.4 carbon material in the net charge. A few of the many aspects of my invention are .425 100.0 illustrated by the following examples, which are y illustrative but not necessarily limitative of the The total. qonversion in this run wais 5815 per cent invention of the original normal hexane. It is evident that Example I the principal reaction occurring in this test run was isomerization of normal hexane to isohexanes ,A series "of test runs for reconstructing hydroincluding neohexane and diisopropyl. It is fur- Vcarbons were made in a closed 18 liter steel rether evident from this test run that my invention, actor having a motor driven stirrer. The proinone of its modications, may be applied to the cedure was to charge predetermined quantities production of high yields of neohexane and dilsoof anhydrous hydroiiuoric acid, boron uoride and propyl from less highly-branched hexanes. Such hydrocarbon material to the reactor, to adjust a modication comprises reconstructing normal the reaction temperature by means of a heated hexane and/or methylpentanes in the presence water or oil bath surrounding the reactor, to stir of concentrated hydrofluoric acid containing a the mixture for a suitable reaction time, to withminor proportion of boron iluoride, separating draw the reaction mixture, to separate the hydroneohexane and/or diisopropyl from the resulting carbon products from the catalyst, and to deterreconstructed hydrocarbon material, and recymine the composition and properties of the prodcling other hexanes and heavier hydrocarbons to ucts. The following data Were obtained: the reconstructing step. i

'retNQ 1 2 a I 4 5 l 0 Hydrocarbon charge n-pentane n-pentane n-pentane iso-pentane n-butane xi-butane BF3, weight percentage of H 2. 7 2. 9 3. 5 3. 8 2. 8 3. 3 Temperamre,r 71-90 10e-115 731105 122-120 13s-144 isi-114 Time, min 34 19 10 225 48 45 Composition of product, weight percentagg'ropaue 0 0 2. 1 1. 1 0 0 isobutane 24. 3 3l` 0 36. v1 34. 2 4. 8 l0. 8 n butane 1. 2 3. 2 9. 9 6. 7 95. 2 88. '1' isopentane.. 19. l 20. 4 20. 9 20. 5 Y n-pentane 29. 8 15. 5 5. 8 3. 7 0 05 hexanes and heaver i- 25.6 29.9 25,2 33.8

Total Conversion, weight percentage 70.2 84. 5 94.2 79.5 44 8 11 3 Composition ofhexanes aud heavier,

volume percentage:

neohexane 12 25 o disopropyl v 38 5 other hexanes 31 25 is ii i0 heavier 14 11 Penine free aviation fraction (336 F. cut

p0Yield. volume percentageliexanes and heavier-4.". 97.6 95.2 97.3 97.9 Gravity, A. P. :78.0 72. 2 ree 71.0 Octane No., A. S. T. M.

y Clear 71.8 '71.8 68.0 73.8 i ce. ses 85.8 v `07.7

ain hydrocarbons to isomers and/or to hydrof4 carbons of higher and] or lower molecular weights.

Example III f .In another test run, normal. hexane. wasre,

'.mnStructed under conditions similar to those 9 of -Example II .except-that .the temperature was 260.-F.-andtheitimewas 35'minutes. Theresulting hydrocarbon was found to havethe following composition Weight percent The totalconversion inthis runwas .9621,per cent of the original normal hexane. The conditions for this run were more drastic than will usually be desired, .since .it is not usually desirable to produce .such larger proportions of propane. It is evidentfrom this run, however,.that at'asomewhat lowertemperature and/ or ashorter treaction.l time .high conversion of normal hexane to isobutane, isopentane, and isohexanes may be obtained. To produce neohexane drastic conversion Vconditions are .especially .eifective, and recycling to the reaction zone of C4 and/or C5 hydrocarbo-ns, and if Adesired hexanes and other par-ailn fractions boiling somewhat above neohexane; these hydrocarbons result as side ...prod- -uctsunder neohexane-producing conditions.

.Alfreshafeed conversion stock `primarily pentanes, as inExample I, `or hexanesor .a mixture is .also suitable for -neohexane production.A

t"Example IV Normal pentane was reconstructed in a 'series of continuous runsmade in a reactor provided with amechanically driven stirrer. The volumes of "hydrocarbon and of catalyst in. the reactor were Vapproximately equal. hydrofluoric acid containing approximately 3 per cent'by weight of boron uoride. After 'a desired average contact or reaction time, the reaction mixturejpassed to a'settler, from which the catavlystfphase was recycled tothe reactor and "from lwhich 'the hydro-carbon phase was removed for examination 'and analysis. Make-up hydro- 'fluoric'acidland/.or yboron uoride were added duringthe'runs. After each run, the .reactor was ihspectedfor the 'presence 'ofsludge The 'in- 'ventionwaspracticed in vruns I and 3 by'saturatin'g' the ingoing'no'rmal pentaneiwithA water; data "for runs "2 .and 4, "in .which water'wa's excluded "(the pentanewas dried 'with Drierite'), are ineluded for comparison.

The catalyst was' lo Example V .Dimethylcyclopentane vsaturated with water was vagitated for 47 minutes at 185011.y and 275 p. s. i. with approximately twice its volume yof hydroliuoricacid ycontaining 1.5 to 1-.6 ,mol. per cent of boron fluoride. The hydrocarbon phase then hadthe following compositioninper cent by Weight:

Propane and lighter 7.4 Isobutane 15.4 Isopentane l5.2 n-Pentane 2.7

Hexanes 3.3 Dimethylcyclopentane 3.8 Intermediate-cyclic .cut 1018 Methylcyclohexane v32;2 I-Ieavier .19.2

No apparent sludge formation ."occurred.

EampZe'VI Normal :hexane saturated with water was mixed with `approximately its own volume ofgamixture of -hydrofluoric acid and approximately .3 {.per `cent of boronl uoridefina B-cc. cOntinuOusreactor havinga 1750-R. 2P.. M. 'stirrer rotating inside fstationary blades. Make-up 2boron fluoride was added intermittently to vreplace that rlost from the system or inactivatedvvThe .reaction mixture effluent vfrom the reactor was cooled and allowedv to settle into `hydrocarbon 'and l`catalyst phases. "The catalystphase -was lrecycled to the reactor, andthe hydrocarbon'phase was withdrawn for examination. Datalfor therunxare:

ItA will tbe appreciated that'various modifications of my invention may bepracticed wthouttdeparting Vfrom the 'spirit ofthe disclosureanddiscussion `or from the scope of the claims.

Comparison of the results of the bat'chrunf Example II with those of the continuousrun f Example VI indicates that formationof relatively light products in the batchrun'was suppressedfby :hydrogen liberated by corrosion of thesteelpressureyessel.

I claim:

1. A process for isomerizing -a llow-"boilingparalinhydrocarbon having at least four carbonatoms per molecule, which comprises continuously "subjecting ina reactionzone a stream of .a saturated hydrocarbon `material `comprising such 'a low-boiling paraflin *hydrocarbon `to the catalytic action of concentratedliquid hydrofluoric acid as the 'eiective catalyst together with "boronluoride in an kamount between about 1i and'about 10 'per cent by weightv of said 'hydrouoric acid,"s`aid liquid hydrouorc acid containing water'inan amount between about 0.05 and about '1.0`1per "cent byweig'ht theref=au'd less :than thatmole'cr4'lunder l'isomerization 'conditionsfo'f temperature,

pressure and time to produce a parain hydrocarbon isomeric with' the first said parain hydrocarbon, continuously withdrawing ahydrocarbon stream from said reaction zone and recovering therefrom a fraction containing a paraffin hydrocarbon so produced, and continuously adding to said reaction zone water in an amount sufficient to maintain the concentration thereof in said catalyst within the aforesaid range.

, 2. A process for isom'erizing a low-boilingcycloparaflin having at least six carbon atoms per moleculef'which comprises continuously subjecting vin a reaction zone a' stream of a saturated hydrocarbon material comprising such a lowboiling cycloparain hydrocarbon to the cataf lytic action of concentrated liquid hydroiluoric acid asthe effective catalyst together with boron trifiuoride in an amount between about 1 and about 10 Vvper cent by `weight of said hydrouoric acid, said liquid hydrofluoric acid containing water in an amount between about 0.05 and about 1.0 per cent by Weight thereof and less than that molecularly equivalent to the boron trifluoride present, under isomerization conditions of temperature, pressure and time to produce a cycloparaftln Vhydrocarbon isomeric with the first said cycloparan'hydrocarbon, continuously withdrawing a hydrocarbonstream from said reaction zone and recovering therefrom a fraction containing a'cycloparaiiln hydrocarbon so produced, and continuously adding to said reaction zone water-in an amount sumcient to maintain the concentration' thereof in said catalyst within the aforesaid range.`

3. A process for converting a vhexane to other paraffin hydrocarbons including Aat least one isomeric hexane, which comprises continuously subjecting in a reaction zone a stream of a hexane to the action of a catalystcomprising essentially liquid` concentrated hydroiiuoric acid associated lwith boron triflu'oride in an amount between about 0.1 and about 10 per cent by weight of said hydroiluoric acid, said liquid hydroiiuoric acid containing water in an amount between about 0.05 and about 1.0 per cent byweightI uoric acid in liquid phase and for a time suiiicient to eifect a substantial extent ofconversion of said hexane, to other parain hydrocarbons including at least one isomeric hexane, continuously withdrawing a hydrocarbon stream from said reaction zone and recovering therefrom a fraction containing a paraflin hydrocarbon so produced., and continuously adding to said reaction zone waterin an amount suicient to maintain the concentration thereof in saidcatalyst within the aforesaid range.

4. A process for converting a low-boiling -cyclohexane to other cycloparaffin hydrocarbons including at leastl one cyclopentane having the same number of carbon atoms per molecule, which comprises continuously subjecting in a reaction zone a stream of a saturated hydrocarbon material comprising a low-boiling cyclohexane to the action of a catalyst comprising essentially liquid concentrated hydrofiuoric acid associated with boron fluoride in an amount between about 0.1 and about 10 per cent by weight of said hydrofluoric acid, said liquid hydrofluoric acid lcontaining water in an amount between about 0.05 and about 1.0 per cent by-weight thereof 4and less than that molecularly equivalent to the boron trifluoride present, at a reaction temperature between about 100 and 250 F. under a pressure suilioient to maintain said hydrofluoric acid in liquid phase and for a time suiicient to effect a substantial extent of conversion of said cyclohexane to other cycloparailin hydrocarbons including at least one cyclopentane having the same number of carbon atoms perv molecule, continuously withdrawing a hydrocarbon stream from said reaction zone and recovering therefrom a fraction containing such a cyclopentane as aforesaid so produced, and continuously adding to said reaction zone water in an amount sufficient to maintain the concentration thereof in said catalyst within the aforesaid range.

5. A process for convertingnormal pentane into isobutane, isopentane and isoheXa-nes, which comprises continuously subjecting in a reaction zone a stream of`a saturated hydrocarbon material comprising liquid normal pentane at a conversion temperature to the catalytic action of a liquid catalyst comprising liquid hydrogen uoride as the essential catalyst and boron trifluoride in an amount between about 0.1 and about 5 per cent by weight of said hydrogen fluoride and also water in an amount between about 0.05 and about 1.0 percent by weight and less than that molecularly equivalent to the boron trifluoride present for a time sufcient to eifect a substantial conversion of normal pentane to isobutane, isopentane and isohexane, recovering from eilluents of said conversion a fraction comprising at least one of said isoparaflins so produced,'and continuously adding to said reaction zone water in an amount sufficient to maintain the concentration thereof in said catalyst within the aforesaid range.

6. A process for isomerizing a low-boiling isomerizable saturated hydrocarbon, which cornprises subjecting a liquid saturated hydrocarbonmaterial comprising a low-boiling isomerizable saturated hydrocarbon to isonierization reaction conditions while intimately admixed with a liquid isomerizing catalyst consisting essentially of liquid hydrogen iluoride together `with boron trifluoride in an amount between about 0.1 and about 5 per cent by weight of said hydrogen iluoride and also .together with water in an amount between about 0.05 and about 1 per cent by Weight of said hydrogen fluoride and less thanthat molecularly equivalent to the boron trifluoride present, with a hydrocarbon to catalyst weight ratio in the range of about 0.1:1 to 3:1, to produce a saturated hydrocarbon isomeric with said isomerizable hydrocarbon, and adding water to said reaction mixture during the course of said isomerization reaction in an amount such as to maintain the water content of the reaction mixture within the aforesaid limits.

7. A process for isomerizing a low-boiling isomerizable saturated hydrocarbon, which comthat molecularly equivalent to the boron trifluoride present, with a hydrocarbon to catalyst 13 weight ratio in the range of about 0.1:1 to 3:1, to produce a saturated hydrocarbon isomeric with said isomerizable hydrocarbon, recovering from eilluents of said reaction an isomeric saturated hydrocarbon so produced, and continuously adding to said reaction zone water in an amount sufficient to maintain the concentration thereof in said catalyst within the aforesaid range.

8. The process of claim 6 in which said lowboiling isomerizable saturated hydrocarbon is a paraffin hydrocarbon having at least 4 carbon atoms per molecule. y

9. The process of claim 6 in which said lowboiling isomerizable saturated hydrocarbon is a cycloparaffin having at least 6 carbon'atoms per molecule.

10. A process for isomerizing a low-boiling paraiiin hydrocarbon having at least five carbon atoms per molecule, which comprises subjecting such a parain hydrocarbon to isomerization reaction conditions in the presence of a liquid catalyst consisting of hydrouoric acid and boron trifluoride, the boron trifluoride being present in the catalyst in minor amount, and also of water in an amount between about 0.05 and about 1 per cent by Weight of said hydrouoric acid and less than that molecularly equivalent to the boron uoride present, and adding water to said reaction mixture during the course of said isom erization reaction in an amount such as to maintain the water content of the reaction mixture Within the aforesaid limits.

11. A process for isomerizing a low-boiling parain hydrocarbon having at least five carbon atoms per molecule, which comprises subjecting such a parafn hydrocarbon to isomerization reaction conditions in the presence of a liquid catalyst consisting of hydrouoric acid and boron triuoride, the boron triiiuoride being present in the catalyst inminor amount, and also of water in a minor amount and less than that molecularly equivalent to the boron iiuoride present, and adding water to said reaction mixture during the course of said isomerization reaction in an amount such as to maintain the water content its.

12. A process for isomerizing a low-boiling paraffin -hydrocarbon having at least ve carbon atoms per molecule, which comprises subjecting such a parafn hydrocarbon to isomeri'zation reaction conditions in the presence of a liquid catalyst consisting of hydrofluoric acid and boron triuoride, the boron triiiuoride being present in the catalyst in minor amount, and alsoof water in an amount between about 0.05 and about 1 per cent by weight of said hydrofluoric acid, and adding water to lsaid reaction mixture during the course of said isomerization reaction in an amount such as to maintain the water content of the reaction mixture Within the aforesaid limits.

FREDERICK E. FREY.

REFERENCES CITED The following references are of record in the yiile of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain May 23, 1929 OTHER REFERENCES Simon, Potential Use of Hydrogen Fluoride- Processes, Reprinted from Ind. & Eng. Chem., vol-32, page 178, Feb., 1940.

Number Number o1' the reaction mixture within the aforesaid lim- 

